CHARACTERIZATION OF A RICE GENE INDUCED BY PSEUDOMONAS-SYRINGAE PV SYRINGAE - REQUIREMENT FOR THE BACTERIAL LEMA GENE-FUNCTION

To characterize the acquired resistance response in rice (Oryza sativa) we have cloned cDNAs corresponding to transcripts that accumulate concomitantly with the establishment of induced resistance following leaf infiltration with Pseudomonas syringae pv. syringae. Here we describe the structure and regulation of one of these cDNAs and two homologous genes. The cDNA represents a transcript from one of these genes, Pir7b, and encodes a putative protein that is 70% identical to the one encoded by Pir7a. Both of these proteins contain a lipase sequence motif. While Pir7a was not expressed under any of the circumstances that were checked, transcripts from Pir7b accumulated transiently after infiltration of leaves with P. syringae pv. syringae. In contrast to other defence-related transcripts, the accumulation of Pir76-specific mRNA depended on the lemA gene function of the bacterial strain infiltrated. II did not occur upon treatment of the plants with other resistance-inducing agents. Thus, the Pir7b gene product does not appear to play a role in acquired resistance. Its function is more likely related to a specific property of the inducing P. syringae pv. syringae strains that is under the control of the two-component regulatory system for which lemA encodes the sensor. A hypothesis about this function is discussed.